INTERGROWTH-21st standards for Hadlock's estimation of fetal weight

Predictive ability of fetal growth charts in identifying kindergarten-age developmental challenges: a cohort study

BACKGROUND

The Society for Maternal-Fetal Medicine recommends defining fetal growth restriction as an estimated fetal weight or abdominal circumference <10th percentile of a population-based reference. However, because multiple references are available, an understanding of their ability to identify infants at increased risk due to fetal growth restriction is critical. Previous studies have focused on the ability of different population references to identify short-term outcomes, but fetal growth restriction also has longer-term consequences for child development.

OBJECTIVE

This study aimed to estimate the association between estimated fetal weight percentiles on the INTERGROWTH-21st and World Health Organization fetal growth charts and kindergarten-age childhood development, and establish the charts' discriminatory ability in predicting kindergarten-age developmental challenges.

STUDY DESIGN

We conducted a retrospective cohort study linking obstetrical ultrasound scans conducted at BC Women's Hospital, Vancouver, Canada, with population-based standardized kindergarten test results. The cohort was limited to nonanomalous, singleton fetuses scanned at ≥28 weeks' gestation from 2000 to 2011, with follow-up until 2017. We classified estimated fetal weight into percentiles using the INTERGROWTH-21st and World Health Organization charts. We used generalized additive modeling to link estimated fetal weight percentile with routine province-wide kindergarten readiness test results. We calculated the area under the receiver-operating characteristic curve and other measures of diagnostic accuracy with 95% confidence intervals at select percentile cut-points of the charts. We repeated analyses using the Hadlock chart to help contextualize findings. The main outcome measure was the total Early Development Instrument score (/50). Secondary outcomes were Early Development Instrument subdomain scores for language and cognitive development, and for communication skills and general knowledge, as well as designation of "developmentally vulnerable" or "special needs".

RESULTS

Among 3418 eligible fetuses, those with lower estimated fetal weight percentiles had systematically lower Early Development Instrument scores and increased risks of developmental vulnerability. However, the clinical significance of differences was modest in magnitude (eg, total Early Development Instrument score -2.8 [95% confidence interval, -5.1 to -0.5] in children with an estimated fetal weight in 3rd-9th percentile of INTERGROWTH-21st chart [vs reference of 31st-90th]). The charts' predictive abilities for adverse child development were limited (eg, area under the receiver-operating characteristic curve <0.53 for all 3 charts).

CONCLUSION

Lower estimated fetal weight percentiles on the INTERGROWTH-21st and World Health Organization charts indicate increased risks of adverse kindergarten-age child development at the population level, but are not accurate individual-level predictors of adverse child development.

Fetal growth restriction and small for gestational age as predictors of neonatal morbidity: which growth nomogram to use?

BACKGROUND

Fetal growth nomograms were developed to screen for fetal growth restriction and guide clinical care to improve perinatal outcomes; however, existing literature remains inconclusive regarding which nomogram is the gold standard.

OBJECTIVE

This study aimed to compare the ability of 4 commonly used nomograms (Hadlock, International Fetal and Newborn Growth Consortium for the 21st Century, Eunice Kennedy Shriver National Institute of Child Health and Human Development-unified standard, and World Health Organization fetal growth charts) and 1 institution-specific reference to predict small for gestational age and poor neonatal outcomes.

STUDY DESIGN

This was a retrospective cohort study of all nonanomalous singleton pregnancies undergoing ultrasound at ≥20 weeks of gestation between 2013 and 2020 and delivering at a single academic center. Using random selection methods, the study sample was restricted to 1 pregnancy per patient and 1 ultrasound per pregnancy completed at ≥22 weeks of gestation. Fetal biometry data were used to calculate estimated fetal weight and percentiles according to the aforementioned 5 nomograms. Maternal and neonatal data were extracted from electronic medical records. Logistic regression was used to estimate the association between estimated fetal weight of <10th and <3rd percentiles compared with estimated fetal weight of 10th to 90th percentile as the reference group for small for gestational age and the neonatal composite outcomes (perinatal mortality, hypoxic-ischemic encephalopathy or seizures, respiratory morbidity, intraventricular hemorrhage, necrotizing enterocolitis, hyperbilirubinemia or hypoglycemia requiring neonatal intensive care unit admission, and retinopathy of prematurity). Receiver operating characteristic curve contrast estimation (primary analysis) and test characteristics were calculated for all nomograms and the prediction of small for gestational age and the neonatal composite outcomes. We restricted the sample to ultrasounds performed within 28 days of delivery; moreover, similar analyses were completed to assess the prediction of small for gestational age and neonatal composite outcomes.

RESULTS

Among 10,045 participants, the proportion of fetuses classified as <10th percentile varied across nomograms from 4.9% to 9.7%. Fetuses with an estimated fetal weight of <10th percentile had an increased risk of small for gestational age (odds ratio, 9.9 [95% confidence interval, 8.5-11.5] to 12.8 [95% confidence interval, 10.9-15.0]). In addition, the estimated fetal weight of <10th and <3rd percentile was associated with increased risk of the neonatal composite outcome (odds ratio, 2.4 [95% confidence interval, 2.0-2.8] to 3.5 [95% confidence interval, 2.9-4.3] and 5.7 [95% confidence interval, 4.5-7.2] to 8.8 [95% confidence interval, 6.6-11.8], respectively). The prediction of small for gestational age with an estimated fetal weight of <10th percentile had a positive likelihood ratio of 6.3 to 8.5 and an area under the curve of 0.62 to 0.67. Similarly, the prediction of the neonatal composite outcome with an estimated fetal weight of <10th percentile had a positive likelihood ratio of 2.1 to 3.1 and an area under the curve of 0.55 to 0.57. When analyses were restricted to ultrasound within 4 weeks of delivery, among fetuses with an estimated fetal weight of <10th percentile, the risk of small for gestational age increased across all nomograms (odds ratio, 16.7 [95% confidence interval, 12.6-22.3] to 25.1 [95% confidence interval, 17.0-37.0]), and prediction improved (positive likelihood ratio, 8.3-15.0; area under the curve, 0.69-0.75). Similarly, the risk of neonatal composite outcome increased (odds ratio, 3.2 [95% confidence interval, 2.4-4.2] to 5.2 [95% confidence interval, 3.8-7.2]), and prediction marginally improved (positive likelihood ratio, 2.4-4.1; area under the curve, 0.60-0.62). Importantly, the risk of both being small for gestational age and having the neonatal composite outcome further increased (odds ratio, 21.4 [95% confidence interval, 13.6-33.6] to 28.7 (95% confidence interval, 18.6-44.3]), and the prediction of concurrent small for gestational age and neonatal composite outcome greatly improved (positive likelihood ratio, 6.0-10.0; area under the curve, 0.80-0.83).

CONCLUSION

In this large cohort, Hadlock, recent fetal growth nomograms, and a local population-derived fetal growth reference performed comparably in the prediction of small for gestational age and neonatal composite outcomes.

The impact of different growth charts on birthweight prediction: obstetrical ultrasound vs magnetic resonance imaging

BACKGROUND

The estimation of fetal weight by fetal magnetic resonance imaging is a simple and rapid method with a high sensitivity in predicting birthweight in comparison with ultrasound. Several national and international growth charts are currently in use, but there is substantial heterogeneity among these charts due to variations in the selected populations from which they were derived, in methodologies, and in statistical analysis of data.

OBJECTIVE

This study aimed to compare the performance of magnetic resonance imaging and ultrasound for the prediction of birthweight using 3 commonly used fetal growth charts: the INTERGROWTH-21st Project, World Health Organization, and Fetal Medicine Foundation charts.

STUDY DESIGN

Data derived from a prospective, single-center, blinded cohort study that compared the performance of magnetic resonance imaging and ultrasound between 36+0/7 and 36+6/7 weeks of gestation for the prediction of birthweight ≥95th percentile were reanalyzed. Estimated fetal weight was categorized as above or below the 5th, 10th, 90th, and 95th percentile according to the 3 growth charts. Birthweight was similarly categorized according to the birthweight standards of each chart. The performances of ultrasound and magnetic resonance imaging for the prediction of birthweight <5th, <10th, >90th, and >95th percentile using the different growth charts were compared. Data were analyzed with R software, version 4.1.2. The comparison of sensitivity and specificity was done using McNemar and exact binomial tests. P values <.05 were considered statistically significant.

RESULTS

A total of 2378 women were eligible for final analysis. Ultrasound and magnetic resonance imaging were performed at a median gestational age of 36+3/7 weeks, delivery occurred at a median gestational age of 39+3/7 weeks, and median birthweight was 3380 g. The incidences of birthweight <5th and <10th percentiles were highest with the Fetal Medicine Foundation chart and lowest with the INTERGROWTH-21st chart, whereas the incidences of birthweight >90th and >95th percentiles were lowest with the Fetal Medicine Foundation chart and highest with the INTERGROWTH-21st chart. The sensitivity of magnetic resonance imaging with an estimated fetal weight >95th percentile in the prediction of birthweight >95th percentile was significantly higher than that of ultrasound across the 3 growth charts; however, its specificity was slightly lower than that of ultrasound. In contrast, the sensitivity of magnetic resonance imaging with an estimated fetal weight <10th percentile for predicting birthweight <10th percentile was significantly lower than that of ultrasound in the INTERGROWTH-21st and Fetal Medicine Foundation charts, whereas the specificity and positive predictive value of magnetic resonance imaging were significantly higher than those of ultrasound for all 3 charts. Findings for the prediction of birthweight >90th percentile were close to those of birthweight >95th percentile, and findings for the prediction of birthweight <5th percentile were close to those of birthweight <10th percentile.

CONCLUSION

The sensitivity of magnetic resonance imaging is superior to that of ultrasound for the prediction of large for gestational age fetuses and inferior to that of ultrasound for the prediction of small for gestational age fetuses across the 3 different growth charts. The reverse is true for the specificity of magnetic resonance imaging in comparison with that of ultrasound.

[Review of the literature on intrauterine and birthweight charts]

OBJECTIVES

To describe the main intrauterine and birthweight charts and review the studies comparing their performance for the identification of infants at risk of adverse perinatal outcomes.

METHODS

We carried out a literature search using Medline and selected the charts most frequently cited in the literature, French charts and those recently published.

RESULTS

Current knowledge on the association between mortality and morbidity and growth anomalies (small and large for gestational age) mostly relies on the use of descriptive charts which describe the weight distribution in unselected populations. Prescriptive charts, which describe ideal growth in low risk populations, have been constructed more recently. Few studies have evaluated whether the thresholds used to identify infants at risk with descriptive charts (such as the 3^rd or the 10^th percentile) are applicable to prescriptive charts. There is a large variability in the percentage of fetuses or newborns identified as being at risk by each chart, with from 3 to 25% having with a weight under the 10^th percentile, regardless of whether descriptive or prescriptive charts are used. The sensitivity and specificity of antenatal screening for small or large for gestational age newborns depends on the chart used to derive estimated fetal weight percentiles.

CONCLUSION

There is marked variability between intrauterine growth charts that can influence the percentage of infants identified as having abnormal growth. These results show that before the adoption of a growth chart, it is essential to evaluate whether it adequately describes the population and its performance for identifying of infants at risk because of growth anomalies.

Developmental Ultrasound Characteristics in Guinea Pigs: Similarities with Human Pregnancy

BACKGROUND

Biometrical and blood flow examinations are fundamental for assessing fetoplacental development during pregnancy. Guinea pigs have been proposed as a good model to study fetal development and related gestational complications; however, longitudinal growth and blood flow changes in utero have not been properly described. This study aimed to describe fetal and placental growth and blood flow of the main intrauterine vascular beds across normal guinea pig pregnancy and to discuss the relevance of this data for human pregnancy.

METHODS

Pregnant guinea pigs were studied from day 25 of pregnancy until term (day ~70) by ultrasound and Doppler assessment. The results were compared to human data from the literature.

RESULTS

Measurements of biparietal diameter (BPD), cranial circumference (CC), abdominal circumference, and placental biometry, as well as pulsatility index determination of umbilical artery, middle cerebral artery (MCA), and cerebroplacental ratio (CPR), were feasible to determine across pregnancy, and they could be adjusted to linear or nonlinear functions. In addition, several of these parameters showed a high correlation coefficient and could be used to assess gestational age in guinea pigs. We further compared these data to ultrasound variables from human pregnancy with high similarities.

CONCLUSIONS

BPD and CC are the most reliable measurements to assess fetal growth in guinea pigs. Furthermore, this is the first report in which the MCA pulsatility index and CPR are described across guinea pig gestation. The guinea pig is a valuable model to assess fetal growth and blood flow distribution, variables that are comparable with human pregnancy.

[Ante- and postnatal growth charts in France - guidelines for clinical practice from the Collège national des gynécologues et obstétriciens français (CNGOF) and from the Société française de néonatologie (SFN)]

OBJECTIVE

To recommend the most appropriate biometric charts for the detection of antenatal growth abnormalities and postnatal growth surveillance.

METHODS

Elaboration of specific questions and selection of experts by the organizing committee to answer these questions; analysis of the literature by experts and drafting conclusions by assigning a recommendation (strong or weak) and a quality of evidence (high, moderate, low, very low) and for each question; all these recommendations have been subject to multidisciplinary external review (obstetrician gynecologists, pediatricians). The objective for the reviewers was to verify the completeness of the literature review, to verify the levels of evidence established and the consistency and applicability of the resulting recommendations. The overall review of the literature, quality of evidence and recommendations were revised to take into consideration comments from external reviewers.

RESULTS

Antenatally, it is recommended to use all WHO fetal growth charts for EFW and common ultrasound biometric measurements (strong recommendation; low quality of evidence). Indeed, in comparison with other prescriptive curves and descriptive curves, the WHO prescriptive charts show better performance for the screening of SGA (Small for Gestational Age) and LGA (Large for Gestational Age) with adequate proportions of fetuses screened at extreme percentiles in the French population. It also has the advantages of having EFW charts by sex and biometric parameters obtained from the same perspective cohort of women screened by qualified sonographers who measured the biometric parameters according to international standards. Postnatally, it is recommended to use the updated Fenton charts for the assessment of birth measurements and for growth monitoring in preterm infants (strong recommendation; moderate quality of evidence) and for the assessment of birth measurements in term newborn (expert opinion).

CONCLUSION

It is recommended to use WHO fetal growth charts for antenatal growth monitoring and Fenton charts for the newborn.

Middle cerebral arterial flow redistribution is an indicator for intrauterine fetal compromise in late pregnancy in low-resource settings: A prospective cohort study

Objective

We aimed to determine the prevalence of abnormal umbilical artery (UA), uterine artery (UtA), middle cerebral artery (MCA) and cerebroplacental ratio (CPR) Doppler, and their relationship with adverse perinatal outcomes in women undergoing routine antenatal care in the third trimester.

Design

Prospective cohort.

Setting

Kagadi Hospital, Uganda.

Population

Non‐anomalous singleton pregnancies.

Methods

Women underwent an early dating ultrasound and a third‐trimester Doppler scan between 32 and 40 weeks of gestation, from 2018 to 2020. We handled missing data using multiple imputation and analysed the data using descriptive methods and a binary logistic regression model.

Main outcome measures

Composite adverse perinatal outcome (CAPO), perinatal death and stillbirth.

Results

We included 995 women. The mean gestational age at Doppler scan was 36.9 weeks (SD 1.02 weeks) and 88.9% of the women gave birth in a health facility. About 4.4% and 5.6% of the UA pulsatility index (PI) and UtA PI were above the 95th percentile, whereas 16.4% and 10.4% of the MCA PI and CPR were below the fifth percentile, respectively. Low CPR was strongly associated with stillbirth (OR 4.82, 95% CI 1.09–21.30). CPR and MCA PI below the fifth percentile were independently associated with CAPO; the association with MCA PI was stronger in small‐for‐gestational‐age neonates (OR 3.75, 95% CI 1.18–11.88).

Conclusion

In late gestation, abnormal UA PI was rare. Fetuses with cerebral blood flow redistribution were at increased risk of stillbirth and perinatal complications. Further studies examining the predictive accuracy and effectiveness of antenatal Doppler ultrasound screening in reducing the risk of perinatal deaths in low‐ and middle‐income countries are warranted.

Tweetable abstract

Blood flow redistribution to the fetal brain is strongly associated with stillbirths in low‐resource settings.

Blood flow redistribution to the fetal brain is strongly associated with stillbirths in low‐resource settings.

This article includes Author Insights, a video abstract available at https://vimeo.com/bjogabstracts/authorinsights17115.

Assessing fetal growth in Africa: Application of the international WHO and INTERGROWTH-21st standards in a Beninese pregnancy cohort

BACKGROUND

Fetal growth restriction is a major complication of pregnancy and is associated with stillbirth, infant death and child morbidity. Ultrasound monitoring of pregnancy is becoming more common in Africa for fetal growth monitoring in clinical care and research, but many countries have no national growth charts. We evaluated the new international fetal growth standards from INTERGROWTH-21st and WHO in a cohort from southern Benin.

METHODS

Repeated ultrasound and clinical data were collected in women from the preconceptional RECIPAL cohort (241 women with singleton pregnancies, 964 ultrasounds). We modelled fetal biometric parameters including abdominal circumference (AC) and estimated fetal weight (EFW) and compared centiles to INTERGROWTH-21st and WHO standards, using the Bland and Altman method to assess agreement. For EFW, we used INTERGROWTH-21st standards based on their EFW formula (IG21st) as well as a recent update using Hadlock's EFW formula (IG21hl). Proportions of fetuses with measurements under the 10th percentile were compared.

RESULTS

Maternal malaria and anaemia prevalence was 43% and 69% respectively and 11% of women were primigravid. Overall, the centiles in the RECIPAL cohort were higher than that of INTERGROWTH-21st and closer to that of WHO. Consequently, the proportion of fetuses under 10th percentile thresholds was systematically lower when applying IG21st compared to WHO standards. At 27-31 weeks and 33-38 weeks, respectively, 7.4% and 5.6% of fetuses had EFW <10th percentile using IG21hl standards versus 10.7% and 11.6% using WHO standards.

CONCLUSION

Despite high anemia and malaria prevalence in the cohort, IG21st and WHO standards did not identify higher than expected proportions of fetuses under the 10th percentiles of ultrasound parameters or EFW. The proportions of fetuses under the 10th percentile threshold for IG21st charts were particularly low, raising questions about its use to identify growth-restricted fetuses in Africa.

Which chart and which cut-point: deciding on the INTERGROWTH, World Health Organization, or Hadlock fetal growth chart

OBJECTIVE

To determine how various centile cut points on the INTERGROWTH-21st (INTERGROWTH), World Health Organization (WHO), and Hadlock fetal growth charts predict perinatal morbidity/mortality, and how this relates to choosing a fetal growth chart for clinical use.

METHODS

We linked antenatal ultrasound measurements for fetuses > 28 weeks' gestation from the British Columbia Women's hospital ultrasound unit with the provincial perinatal database. We estimated the risk of perinatal morbidity/mortality (decreased cord pH, neonatal seizures, hypoglycemia, and perinatal death) associated with select centiles on each fetal growth chart (the 3rd, 10th, the centile identifying 10% of the population, and the optimal cut-point by Youden's Index), and determined how well each centile predicted perinatal morbidity/mortality.

RESULTS

Among 10,366 pregnancies, the 10th centile cut-point had a sensitivity of 11% (95% CI 8, 14), 13% (95% CI 10, 16), and 12% (95% CI 10, 16), to detect fetuses with perinatal morbidity/mortality on the INTERGROWTH, WHO, and Hadlock charts, respectively. All charts performed similarly in predicting perinatal morbidity/mortality (area under the curve [AUC] =0.54 for all three charts). The statistically optimal cut-points were the 39th, 31st, and 32nd centiles on the INTERGROWTH, WHO, and Hadlock charts respectively.

CONCLUSION

The INTERGROWTH, WHO, and Hadlock fetal growth charts performed similarly in predicting perinatal morbidity/mortality, even when evaluating multiple cut points. Deciding which cut-point and chart to use may be guided by other considerations such as impact on workflow and how the chart was derived.

World Health Organization fetal growth charts applied in a French birth cohort

OBJECTIVE

To evaluate the applicability of World Health Organization (WHO) fetal growth charts for abdominal circumference (AC), femur length (FL) and estimated fetal weight (EFW) at the second and third trimester ultrasounds in a French birth cohort.

MATERIALS AND METHODS

Using the ELFE cohort of live births after 33 weeks' gestation in France in 2011, we selected 7747 singletons with fetal biometric measurements at the second (20-25 weeks) and third (30-35 weeks) trimester routine ultrasounds. We calculated proportions of fetuses <3rd and <10th percentiles and >90th and >97th percentiles for AC, FL and EFW using WHO charts and two international (Intergrowth and Hadlock) and two national (Salomon and CFEF) charts. Analyses were also carried out in a subsample of 4427 low-risk births.

RESULTS

WHO charts classified 2,3% and 8-10% of fetuses <3rd and <10th percentiles respectively, for AC and FL in the second and third trimesters and EFW in the third trimester. Similarly, about 3 and 10% of fetuses had AC, FL and EFW >97th and >90th percentile in both trimesters. Hadlock and CFEF charts also provided a good fit for third-trimester EFW <10th percentile. For most measures, Intergrowth yielded low proportions <3rd and <10th percentile, and high proportions >90th and >97th percentiles. Proportions were slightly lower for low-risk pregnancies.

CONCLUSION

WHO charts provided a good description of the distribution of French fetal biometric measures. Further research is needed to assess the impact of using WHO charts on obstetrical management and perinatal outcomes.

Comparison of the performance of estimated fetal weight charts for the detection of small- and large-for-gestational age newborns with adverse outcomes: a French population-based study

OBJECTIVE

To compare the performance of estimated fetal weight (EFW) charts at the third trimester ultrasound for detecting small- and large-for-gestational age (SGA/LGA) newborns with adverse outcomes.

DESIGN

Nationally representative observational study.

SETTING

French maternity units in 2016.

POPULATION

9940 singleton live births with an ultrasound between 30 and 35 weeks of gestation.

METHODS

We compared three prescriptive charts (INTERGROWTH-21st, World Health Organization (WHO), Eunice Kennedy Shriver National Institute of Child Health and Human Development [NICHD]), four descriptive charts (Hadlock, Fetal Medicine Foundation, two French charts) and a French customised growth model (Epopé).

MAIN OUTCOME MEASURES

SGA and LGA (birthweights <10th and >90th percentiles) associated with adverse outcomes (low Apgar score, delivery-room resuscitation, neonatal unit admission).

RESULTS

2.1% and 1.1% of infants had SGA and LGA and adverse outcomes, respectively. The sensitivity and specificity for detecting these infants with an EFW <10th and >90th percentile varied from 29-65% and 84-96% for descriptive charts versus 27-60% and 83-96% for prescriptive charts. WHO and French charts were closest to the EFW distribution, yielding a balance between sensitivity and specificity for SGA and LGA births. INTERGROWTH-21st and Epopé had low sensitivity for SGA with high sensitivity for LGA. Areas under the receiving operator characteristics curve ranged from 0.62 to 0.74, showing low to moderate predictive ability, and diagnostic odds ratios varied from 7 to 16.

CONCLUSION

Marked differences in the performance of descriptive as well as prescriptive EFW charts highlight the importance of evaluating them for their ability to detect high-risk fetuses.

TWEETABLE ABSTRACT

Choice of growth chart strongly affected identification of high-risk fetuses at the third trimester ultrasound.

Unisex vs sex-specific estimated fetal weight charts for fetal growth monitoring: a population-based study

BACKGROUND

In contrast with birthweight or other growth charts, a feature of most intrauterine charts is that they are not differentiated by sex. Differences in weight by sex during pregnancy are considered to be relatively minor; however, small systematic differences may affect the sensitivity and specificity of screening for fetuses with growth restriction.

OBJECTIVE

To assess differences between unisex and sex-specific estimated fetal weight charts at the third-trimester ultrasound with regard to the sex ratio of fetuses detected with an estimated fetal weight <10th percentile and subsequent detection of small-for-gestational-age newborns with morbidity at birth.

STUDY DESIGN

The study included 9940 singleton live births from a French population-based study in 2016. Main outcomes were an estimated fetal weight <10th percentile at the routine third-trimester ultrasound between 30 and 35 weeks of gestation, and small for gestational age infants (birthweight <10th percentile) with neonatal morbidity (Apgar score <7 at 5 minutes and/or resuscitation in delivery room and/or admission to a neonatal unit). We used 2 charts with unisex and sex-specific options: the World Health Organization international standard chart and a customized chart for fetal sex based on Gardosi's gestation-related optimal weight model adapted to the French population (Epopé). Hadlock's unisex chart, commonly used in clinical care and research, was also included to provide an external reference. We compared the proportions of female and male fetuses with an estimated fetal weight <10th percentile and the sensitivity and specificity of such estimated fetal weight for predicting small-for-gestational-age newborns with morbidity when using unisex vs sex-specific charts, overall and by sex.

RESULTS

Among all singleton births, there were 51.6% males and 48.4% females. Males faced higher risks of being small-for-gestational-age with morbidity at birth (2.4% vs 1.8%; P=.031). Using the World Health Organization unisex chart, 6.9% of males and 9.9% of females had an estimated fetal weight <10th percentile vs 9.9% of males and 7.1% of females with the sex-specific chart; these proportions were 3.5% and 4.6% and 4.3% and 2.7%, respectively, for the Epopé. Proportions of estimated fetal weight <10th percentile using Hadlock's chart were slightly higher than those obtained using the unisex World Health Organization chart (7.5% of males and 10.6% of females), but the difference of about 3% was the same. The sensitivity of an estimated fetal weight <10th percentile for identifying small-for-gestational-age newborns with morbidity differed for males and females by type of chart; unisex charts detected more small-for-gestational-age females with morbidity and sex-specific charts detected more small-for-gestational-age males with morbidity, but the overall sensitivity was the same (49.1% for the World Health Organization chart and Hadlock's chart and 34.9% for the Epopé chart).

CONCLUSION

This study suggests that the use of sex-specific charts instead of unisex charts would reduce sex bias in intrauterine growth screening during the third trimester of pregnancy. Prospective studies are needed to assess the effects of using sex-specific charts rather than unisex charts on obstetrical management and outcomes.

The impact of optimal dating on the assessment of fetal growth

BACKGROUND

The impact of using the Intergrowth (IG) dating formulae in comparison to the commonly used Robinson dating on the evaluation of biometrics and estimated fetal weight (EFW) has not been evaluated.

METHODS

Nationwide cross-sectional study of routine fetal ultrasound biometry in low-risk pregnant women whose gestational age (GA) had been previously assessed by a first trimester CRL measurement. We compared the CRL-based GA according to the Robinson formula and the IG formula. We evaluated the fetal biometric measurements as well as the EFW taken later in pregnancy depending on the dating formula used. Mean and standard deviation of the Z scores as well as the number and percentage of cases classified as <3rd, < 10th, >90th and > 97th percentile were compared.

RESULTS

Three thousand five hundred twenty-two low-risk women with scans carried out after 18 weeks were included. There were differences of zero, one and 2 days in 642 (18.2%), 2700 (76.7%) and 180 (5%) when GA was estimated based on the Robinson or the IG formula, respectively. The biometry Z scores assessed later in pregnancy were all statistically significantly lower when the Intergrowth-based dating formula was used (p < 10- 4). Likewise, the number and percentage of foetuses classified as <3rd, < 10th, >90th and > 97th percentile demonstrated significant differences. As an example, the proportion of SGA foetuses varied from 3.46 to 4.57% (p = 0.02) and that of LGA foetuses from 17.86 to 13.4% (p < 10- 4).

CONCLUSION

The dating formula used has a quite significant impact on the subsequent evaluation of biometry and EFW. We suggest that the combined and homogeneous use of a recent dating standard, together with prescriptive growth standards established on the same low-risk pregnancies, allows an optimal assessment of fetal growth.

Diagnostic accuracy of fetal growth charts for placenta-related fetal growth restriction

INTRODUCTION

The choice of fetal growth chart to be used in antenatal screening for fetal growth restriction (FGR) has an important impact on the proportion of fetuses diagnosed as small for gestational age (SGA), and on the detection rate for FGR. We aimed to compare diagnostic accuracy of SGA diagnosed using four different common fetal growth charts [Hadlock, Intergrowth-21st (IG21), World Health Organization (WHO), and National Institute of Child Health and Human Development (NICHD)], for abnormal placental pathology.

METHODS

A secondary analysis of data from a prospective cohort study in low-risk nulliparous women. The exposure was SGA (birthweight <10th centile for gestational age) using each of the four charts. The outcomes were one of three types of abnormal placental pathology associated with fetal growth restriction: maternal vascular malperfusion (MVM), chronic villitis, and fetal vascular malperfusion.

RESULTS

A total of 742 nulliparous women met the study criteria. The proportion of SGA was closest to the expected rate of 10% using the Hadlock chart (12.7%). The detection rates (DR) and false positive rates (FPR) for MVM pathology were similar for the Hadlock (DR = 53.1%, FPR = 10.8%), WHO (DR = 59.4%, FPR = 14.2%), and NICHD (DR = 53.1%, FPR = 12.3%) charts, and each was superior when compared to the IG21 chart (DR = 34.4%, FPR = 3.8%, p < 0.001). The diagnosis of SGA was associated with increased risks of preeclampsia and preterm birth for all four charts.

DISCUSSION

The selection of fetal growth chart to be used in screening programs for FGR has important implications with regard to the false positive and detection rate for FGR.

Application of new fetal growth standards in a multiethnic population

OBJECTIVES

Ultrasound assessment of fetal growth is essential to reduce adverse pregnancy outcomes. Intergrowth-21st developed international standards. Currently, we use in France chart based on Hadlock's formula. This study aims to evaluate, the impact of switching from national curves to IG-21 curves or a combination of IG-21 with Hadlock.

METHODS

The study population consisted of 3 697 singleton pregnancies with fetal biometry measured between 22 and 38 weeks of gestation. Z-scores were calculated for each biometry according to CFEF and IG-21. The estimated fetal weight and its Z-score were calculated using the Hadlock formula and IG-21 formula.

RESULTS

We observed 21% of head circumference, 9% of abdominal circumference and 7% of femoral length below the 10th centile with Intergrowth-21. Concerning estimated fetal weight, IG-21 classified 13.8% fetuses as SGA, IG-21/Hadlock 10.8% and CFEF 16.1%. Between 36 and 38 weeks of gestation, IG-21 classified more fetuses as SGA than IG-21/Hadlock and CFEF, respectively 18%, 14.1% and 13.3%.

CONCLUSION

The use of IG-21 or IG-21/Hadlock in the general population would lower the number of fetuses classified as SGA except for fetuses between 36 and 38 weeks. During this period, many decisions of induced early delivery or specific management are established to prevent adverse perinatal outcome. Those results must be supplemented by a comparison to newborns' weight.